In a typical cellular radio access network (RAN), an area is divided geographically into a number of coverage areas or regions (namely, cells and cell sectors). The coverage areas are defined by radio frequency (RF) radiation patterns from base stations (for example, eNodeBs and base transceiver stations (BTSs)). The base stations in a region may be communicatively linked with a control node that manages certain operations of the base stations and that may function generally as an aggregation point for communications passing through the base stations. The control node may also provide or facilitate connectivity and/or communication with a transport network such as the public switched telephone network (PSTN) or the Internet. Generally, the control node may include one or more components communicatively linked to each other, for example, mobility management entities (MMEs), serving gateways (S-GWs), packet gateways (P-GWs), RAN controllers, mobile switching centers (MSCs), and packet data serving nodes (PDSNs). Other examples are possible as well.
When a mobile station (such as a cellular telephone, pager, or appropriately equipped portable computer, for instance) is positioned in a coverage area of such a network, the mobile station communicates via an RF air interface with base station antennas that radiate to define the coverage area. Consequently, a communication path may be established between the mobile station and the transport network, via the air interface, the base station, and the control node.
In practice, communications over the air interface between a base station and a mobile station will comply with a defined air interface protocol or access technology. Numerous such protocols are well known in the art, and others will be developed in the future. Examples of existing protocols include CDMA (e.g., 1xRTT, 1xEV-DO), Long-Term Evolution (LTE), WiMax, iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, microwave, satellite, MMDS, Wi-Fi, and Bluetooth.
In general, when the control node encounters a trigger event that indicates a need to transmit information to a given mobile station, the control node may cause one or more base stations to page the mobile station. For instance, the control node may initiate paging in the coverage area where the mobile station was last registered and in one or more coverage areas surrounding that coverage area, out to a particular radius that defines a paging area. If the mobile station responds to the page, then the control node would thereby identify the coverage area in which the mobile station is currently operating, and the control node may arrange for transmission of the information to the mobile station in that coverage area.
In each wireless coverage area, the air interface defined by the serving base station may be divided into various discrete channels by applying one or more mechanisms, such as unique spread-spectrum coding, time division multiplexing, and/or frequency differentiation, for instance. One or more of the channels in each coverage area may be reserved for use as a paging channel, on which the base station may broadcast page messages destined to particular mobile stations. And one or more of the channels in each coverage area may be reserved for use as an access channel, on which mobile stations may transmit page response messages to the base station. In practice, when a base station receives from a control node a directive to page a mobile station, the base station may responsively broadcast on the paging channel a page message directed to that mobile station. If and when the mobile station receives the page message, the mobile station may then programmatically transmit a page response message to the base station on the access channel.